open system call using c program | os cs8461 | 4th sem of cse | operating system lab | QT
operating system laboratory for cse engineering playlist
• Operating System
Exp# 2f open system call
Date :
Aim
To create a file and to write contents.
open()
Used to open an existing file for reading/writing or to create a new file.
Returns a file descriptor whose value is negative on error.
The mandatory flags are O_RDONLY, O_WRONLY and O_RDWR
Optional flags include O_APPEND, O_CREAT, O_TRUNC, etc
The flags are ORed.
The mode specifies permissions for the file.
creat()
Used to create a new file and open it for writing.
It is replaced with open() with flags O_WRONLY|O_CREAT | O_TRUNC
Algorithm
1. Declare a character buffer buf to store 100 bytes.
2. Get the new filename as command line argument.
3. Create a file with the given name using open system call with O_CREAT and
O_TRUNC options.
4. Check the file descriptor.
a) If file creation is unsuccessful, then stop.
5. Get input from the console until user types Ctrl+D
a) Read 100 bytes (max.) from console and store onto buf using read system call
b) Write length of buf onto file using write system call.
6. Close the file using close system call.
7. Stop